The mafia has become widespread in America, leading to frequent assassinations on the streets. Inferno, a mysterious corporation, is responsible for many of these crimes through their use of an unbeatable human weapon called "Phantom." On one occasion, a Japanese tourist unintentionally witnesses Phantom's latest murder and tries to flee by hiding in a secluded building. However, Ein, the leader of Inferno, captures the tourist and brainwashes him into forgetting his past identity as "Zwei," becoming a puppet controlled by Inferno with no recollections. Now Zwei is trapped in a world of lies, deception, and violence, fighting to stay alive while hoping one day to regain his memories and break free from this dangerous environment where he's always at risk of death.